The rate of human invention is faster, and the rate of cultural loss is slower, in areas occupied by many competing societies with many individuals and in contact with societies elsewhere.

Measles and TB evolved from diseases of our cattle, influenza from a disease of pigs, and smallpox possibly from a disease of camels. The Americas had very few native domesticated animal species from which humans could acquire such diseases.

In fact, everywhere in the world there has been a flux between big and small societies. Big political units are constantly being formed, later to fragment. The individual pieces try to pull apart, and then they join together again. One sees that in Europe: There have been unifications and then dissolutions and reunifications. So in the long run, it's 10,000 steps toward amalgamation offsetting 9,999 steps toward falling apart again. In businesses and industries, I would guess that's also true.

History as well as life itself is complicated -- neither life nor history is an enterprise for those who seek simplicity and consistency.

Our biggest threat is not an asteroid about to crash into us, something we can do nothing about. Instead, all the major threats facing us today are problems entirely of our own making. And since we made the problems, we can also solve the problems.

In much of the rest of the world, rich people live in gated communities and drink bottled water. That's increasingly the case in Los Angeles where I come from. So that wealthy people in much of the world are insulated from the consequences of their actions.

The United States has long thought of itself as the land of infinite plenty, and historically we did have abundant resources. But now we are gradually exhausting our fisheries, our topsoil, our water. On top of that, we're coming to the end of world resources.